It is common to have a plurality of devices, each requiring bandwidth, in a system having bandwidth limitations. An example of such system is a surveillance system comprising 10 monitoring devices. The total bandwidth available in the surveillance system may for example be 100 Mbit/s. In such systems, it is known to manually set an upper bandwidth limit for each monitoring device so that a total upper bandwidth limit of the monitoring device does not exceed the 100 Mbit/s limitation, for example by assigning each monitoring device with an upper bandwidth limit of 10 Mbit/s. In this case, each monitoring device will typically have its own bitrate controller which may be set to regulate the encoding of monitoring data acquired by the monitoring device to be transmitted to not exceed the assigned 10 Mbit/s limit. The bitrate of the monitoring data may be lowered by either encoding the monitoring data using a higher compression ratio, or by discarding bits of the monitoring data (e.g. skip frames in an image stream). When the bitrate of the monitoring data is lowered, a reduction in bitrate for the monitoring data, compared to the bitrate that would be required to transmit the originally acquired monitoring data, is increased. However, depending on the monitoring data acquired by the monitoring device, it may be advantageous to adapt the upper bandwidth limit such that the bitrate reduction of the encoded monitoring data may be lower or higher. This requires that the upper bandwidth limits of the monitoring devices can be adjusted.
US 2012/0218416 (Thales) relates to a dynamically reconfigurable video surveillance system which includes at least one video camera, a remote server, at least one viewing terminal. The video camera or cameras include means for compressing the video sequences captured, and the compression ratio is dynamically adaptable by taking into account a control messages originating from the remote server. The control message may include a priority level associated by the remote server with each video streams received originating from the camera or cameras of the system. The priority level is determined by the remote server as a function of the signalling information representative of the activity detected and forwarded by the video camera or cameras to the remote server, or determined by each of the video cameras. Such a system 100 is schematically described in FIG. 1, wherein the remote server 102 may send control messages to any of the video cameras 104a-d for adapting the compression ratio to be used by the video cameras 104a-d. The control message may be dependent on priority levels computed by the video cameras and dependent on activity detected by each of the cameras. These priority levels are transmitted by the video cameras 104a-d to the remote server 102.
However, the video surveillance system in US 2012/0218416 is complex and do not consider the case where all or many of the video cameras has a high priority level.